The present invention relates to magnetostrictive devices effected by magnetic fields, and more particularly, to magnetostrictive optical fiber cables and magnetic field detectors.
Magnetic field measuring devices, including magnetometers, are well known and include moving and stationary coils, Hall effect devices, thin films, fluxgates, magnetic resonance devices, and superconducting devices. However, the need exists for a low cost device having high sensitivity. The most recent advance in magnetic field detection devices such as SQUID (Superconducting Qllantum Interference Device) devices require cryogenic temperatures for operation and thus have an accompanying high cost of materials and complex apparatus requirements.
Prior art optical devices for detecting magnetic fields make use of the Faraday effect which is based on the measurements of the extent of rotation of circularly polarized light dependent upon the prevailing magnetic field. Devices using the Faraday effect are exemplified in the U.S. Pat. Nos. 3,936,742 of Krause, 3,621,390 of Von Willisen, and 3,257,608 of Bell et al. The Faraday effect devices have low sensitivity and consequently have a poor signal to noise (S/N) ratio. Accordingly, it is desirable to provide a magnetic field detector which is low cost, simple to construct, does not require costly and cumbersome apparatus, can be used at room temperatures, and provides a very high sensitivity to weak magnetic fields and thus a correspondingly high signal to noise ratio.